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Published on: May 28, 2019
Lactate and pH as Independent Biomarkers for Prognosticating Meaningful Post-out-of-Hospital Cardiac Arrest Outcomes:
Nishil T Patel1,2, Casey T Carr3,4, Charlotte M Hopson1
1Department of Emergency Medicine, University of Florida, Gainesville, FL 32610, USA.
Insights
Lactate and pH levels are key predictors of survival and neurological outcomes after out-of-hospital cardiac arrest (OHCA). Higher pH and lower lactate levels correlate with better survival and neurological function post-OHCA.
Area of Science:
- Biomedical Science
- Clinical Medicine
- Emergency Medicine
Background:
- Out-of-hospital cardiac arrest (OHCA) is a critical medical emergency with significant mortality and morbidity.
- Predicting patient outcomes after OHCA is crucial for guiding treatment and resource allocation.
- Lactate and pH are commonly measured biomarkers in cardiac arrest but their predictive utility requires systematic evaluation.
Purpose of the Study:
- To systematically review and characterize the predictive value of lactate and pH for survival and neurological outcomes in OHCA patients.
- To synthesize existing evidence on the relationship between pre-hospital lactate and pH levels and patient outcomes.
- To establish thresholds for these biomarkers associated with favorable and unfavorable outcomes.
Main Methods:
- A systematic literature review adhering to PRISMA guidelines was conducted.
- Searches were performed across major databases including PubMed, Embase, Web of Science, Cochrane Central, and Academic Search Premier.
- Meta-analyses were used to quantify the association between lactate/pH and survival/neurological outcomes in adults with OHCA, excluding in-hospital arrests and ROSC prediction studies.
Main Results:
- The review included 49 studies encompassing 21,120 patients, predominantly OHCA cases.
- Mean lactate levels of 7.24 and 7.15 were associated with favorable survival and neurological outcomes, respectively.
- Mean pH levels of 7.22 were linked to both favorable survival and neurological outcomes. Higher lactate and lower pH correlated with poorer outcomes.
Conclusions:
- A direct correlation exists between pH and favorable survival and neurological outcomes; higher pH indicates better outcomes.
- An inverse relationship was observed between lactate levels and outcomes; higher lactate levels are associated with poorer survival and neurological function.
- The lactate threshold for survival appears more lenient than that for favorable neurological outcome.
Abstract:
Background/Objectives: To systematically review the literature and to characterize the utility of lactate and pH for predicting survival and long-term neurological outcomes after out-of-hospital cardiac arrest (OHCA). Methods: PRISMA guidelines were followed. PubMed, Embase, Web of Science, Cochrane Central, and Academic Search Premier were searched for relevant studies. The population included adults with OHCA. Studies with majority in-hospital cardiac arrest (>50%) and studies predicting return of spontaneous circulation (ROSC) were excluded. Pairs of investigators reviewed the studies for relevance. Data were extracted and risk of bias was assessed using the Newcastle-Ottawa Scale. Meta-analyses were performed to characterize the relationship between lactate and pH with survival and neurological outcomes. Results: We included 21,120 patients over 49 studies. Most studies (78%) included OHCA only. Mean lactate of 7.24 (95%CI:6.05-8.44) was associated with favorable survival (n = 9155; 21 studies), while mean lactate of 7.15 (95%CI:6.37-7.93) was associated with favorable neurological outcome (n = 7534; 21 studies). Mean pH of 7.22 (95%CI:7.10-7.33) was associated with favorable survival (n = 4077; 7 studies), while a mean pH of 7.22 (95%CI:7.17-7.27) was associated with favorable neurological outcome (n = 6701; 13 studies). Poor outcomes were associated with lower pH and higher lactate values. Risk of bias was generally low to medium, while heterogeneity was high. Conclusions: A direct correlation exists between pH with survival and neurological outcome; the likelihood of favorable outcomes increases as pH increases. Conversely, an inverse relationship exists between lactate with survival and neurological outcome; higher lactate is associated with poorer outcomes. For lactate, the threshold for survival was more lenient than for favorable neurological outcome.
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